The present invention generally relates to the field of chemical mechanical polishing. More particularly, the present invention is directed to a chemical mechanical polishing pad having a process-dependent groove configuration.
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting and dielectric materials are deposited onto and etched from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modem wafer processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PIECED) and electrochemical plating. Common etching techniques include wet and dry isotropic and anisotropic etching, among others.
As layers of materials are sequentially deposited and etched, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., photolithography) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful for removing undesired surface topography as well as surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches and contaminated layers or materials.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize workpieces, such as semiconductor wafers. In conventional CMP using a dual-axis rotary polisher, a wafer carrier, or polishing head, is mounted on a carrier assembly. The polishing head holds the wafer and positions the wafer in contact with a polishing layer of a polishing pad within the polisher. The polishing pad has a diameter greater than twice the diameter of the wafer being planarized. During polishing, each of the polishing pad and wafer is rotated about its concentric center while the wafer is engaged with the polishing layer. The rotational axis of the wafer is offset relative to the rotational axis of the polishing pad by a distance greater than the radius of the wafer such that the rotation of the pad sweeps out a ring-shaped “wafer track” on the polishing layer of the pad. The width of the wafer track is equal to the diameter of the wafer when the only movement of the wafer is rotational. However, in some dual-axis polishers, the wafer is oscillated in a plane perpendicular to its axis of rotation. In this case, the width of the wafer track is wider than the diameter of the wafer by an amount that accounts for the displacement due to the oscillation. The carrier assembly provides a controllable pressure between the wafer and polishing pad. During polishing, a slurry, or other polishing medium, is flowed onto the polishing pad and into the gap between the wafer and polishing layer. The wafer surface is polished and made planar by chemical and mechanical action of the polishing layer and slurry on the surface.
The interaction among polishing layers, polishing slurries and wafer surfaces during CMP is being increasingly studied in an effort to optimize polishing pad designs. Most of the polishing pad developments over the years have been empirical in nature. Much of the design of polishing surfaces has focused on providing these surfaces with various patterns of voids and networks of grooves that are claimed to enhance slurry utilization and polishing uniformity. Over the years, quite a few different groove and void patterns and configurations have been implemented. Prior art groove patterns include radial, concentric circular, Cartesian grid and spiral, among others. Prior art groove configurations include configurations wherein the depth of all the grooves are uniform among all grooves and configurations wherein the depth of the grooves varies from one groove to another.
Some designers of rotational CMP pads have disclosed pads having grooves of two or more configurations that change from one configuration to another based on one or more radial distances from the center of the pad. These pads are touted as providing superior performance in terms of polishing uniformity and slurry utilization, among other things. For example, in U.S. Pat. No. 6,520,847 to Osterheld et al., Osterheld et al. disclose several pads having three concentric ring-shaped regions, each containing a configuration of grooves that is different from the configurations of the other two regions. The configurations vary in different ways in different embodiments. Ways in which the configurations vary include variations in number, cross-sectional area, spacing and type of grooves.
Although pad designers have heretofore proposed CMP pads that include two or more groove configurations that are different from one another based on one or more radial distances from the concentric centers of such pads, these designs do not directly consider the rotational rates of the wafer being polished and the pad. Consequently, there is a need for CMP polishing pad designs that are optimized, at least in part, based on the rotational rate of the article being polished and the rate the pad is moved relative to the article.